T1 L13: Heart Failure

• Definition of heart failure?

  a state that develops when the heart fails to maintain an adequate cardiac output to meet the demands of the body
• Systolic heart failure?

  impaired ability of the heart to eject blood
• Diastolic heart failure?

  impaired ability of the ventricles to fill with blood
• At rest, cardiac output is typically..?

  70 mLs/kg/min
• Three factors affecting stroke volume?

  Preload, afterload, contractility
• Increased heart rate results in increased cardiac output, until..?

  causes cardiac output to fall, as excessively high heart rate doesn't allow ventricles to fill with blood properly
• Preload is affected by?

  venous blood pressure

  volume of circulating blood
• Preload increases with?

  increasing blood volume and vasoconstriction
• Preload decreases with?

  blood volume loss and vasodilatation
• Frank-Starling Law?

  "An increase in volume of blood filling the heart stretches the heart muscle fibres, causing greater contractile forces which, in turn, increases stroke volume."

  is true until a certain point; at some stage the fibres become over-stretched and the force of contraction is reduced.
• Greater the aortic/pulmonary pressure, greater the afterload.
• Afterload increases with?

  hypertension and vasoconstriction
• Afterload decreases with?

  vasodilatation
• Relationship between afterload and cardiac output?

  As afterload increases, cardiac output decreases.
• High vs low output heart failure?

  low output heart failure: systolic heart failure, diastolic heart failure (caused by impairments to the heart)

  high output heart failure: heart cannot keep up with the unusually high demands on cardiac output due to other medical conditions (heart works normally). Could be due to: thyrotoxicosis, profound anaemia, pregnancy, pagets disease, sepsis
• Ejection fraction?

  percentage of blood pushed out of the heart every time it contracts (around 60%)
• HFREF?

  heart failure with reduced ejection fraction (systolic heart failure)
• HFPEF?

  heart failure with preserved ejection fraction (diastolic heart failure)
• Systolic heart failure (HFREF / heart failure with reserved ejection fraction)?

  progressive deterioration of myocardial contractile function. Heart cannot push blood out.

  Caused by:

  ischaemic injury of heart muscle

  volume overload

  pressure overload
• Diastolic heart failure (HFPEF/ heart failure with preserved ejection fraction)?

  inability of the heart chamber to relax, expand and fill sufficiently during diastole to accommodate an adequate blood volume.

  'stiff heart'

  can be caused by:

  significant left ventricular hypertrophy

  infiltrative disorders

  constrictive pericarditis

  restrictive cardiomypathy
• Causes of heart failure?

  coronary heart disease

  hypertensive heart disease

  valvular heart disease

  myocardial disease / cardiomyopathies

  congenital heart disease
• Cardiomyopathies?

  disease of the heart muscle
• Types of cardiomyopathies?

  • Dilated cardiomyopathy (various causes, eg drug toxicity, myocarditis, pregnancy, systemic disease, muscular dystrophies)
  • hypertrophic cardiomyopathy (hereditary)
  • restrictive cardiomyopathy (rare - main cause amyloid (disease where too much protein is made))
• Compensatory mechanisms for heart failure?

  • Frank Starling mechanism (vasoconstriction, increased venous return to heart, increased preload, heart muscle stretch, more contractility)
  • Myocardial structural change (hypertrophy)
  • Activation of neurohormonal system:
  • Noradrenaline release (increase heart rate, myocardial contractility, vasoconstriction)
  • ANP/BNP release
  • RAAS system activation
• RAAS (Renin-Angiotensin-Aldosterone System)?

  liver (organ) → Angiotensinogen (hormone precursor) -- RENIN (activating enzyme) from kidney (organ) --> Angiotensin I (hormone) -- ACE (activating enzyme) from kidney (organ) and lungs (organ) --> Angiotensin II (hormone).

  
  

  Angiotensin II acts on:

  • pituitary gland: release ADH (hormone), decreased diuresis, water retention
  • adrenal gland: release aldosterone (hormone), decreased natriuresis (less salt lost), water retention
  • Arterioles → vasoconstriction
  • parasympathetic activity
• NP (natriuretic peptide) system?

  Enlarged ventricular wall → pro BNP (B-type natriuretic peptide) released → converted to BNP

  BNP acts:

  • diuresis
  • vasodilatation
  • RAAS inhibition
  • SNS (sympathetic nervous system) inhibition

  hence brings BP down. However, issue:

  it is inactivated very quickly, half life 20 minutes
• Natriuretic peptide can be used as a test for heart failure.
• Clinical types of heart failure?

  • left sided, right sided or biventricular heart failure
  • acute and chronic heart failure
  • compensated and decompensated heart failure
• Left sided heart failure?


  blood backs up progressively from left atrium to pulmonary circulation

  causes:

  • ischaemic heart disease
  • hypertension
  • valvular heart disease
  • myocardial disease
• Effects of left ventricular heart failure on lungs?

  pressure in pulmonary vein transmitted to capillaries and arteries

  leads to pulmonary congestion and oedema

  'heavy, wet lungs':

  • Dyspnoea (breathlessness) following exertion
  • Orthopnoea (breathlessness lying flat; relieved by sitting/standing)
  • Paroxysmal nocturnal dyspnoea (orthopnoea with attacks of exreme dyspnoea occuring at night)
• Effects of left ventricular heart failure on kidneys?

  decreased cardiac output causes reduction in renal perfusion

  activation of RAAS

  retention of salt and water, expansion of interstitial fluid and blood volumes
• Effects of left ventricular heart failure on the brain?

  hypoxic encephalopathy (brain function altered due to low oxygen)

  irritability

  loss of attention

  restlessness

  stupor / coma
• Right sided heart failure?

  usually as a consequence of left sided heart failure

  cor pulmonale: enlargement of right side of heart due to pulmonary hypertension

  usually result of respiratory diseases eg COPD or pulmonary emboli
• Systemic effects of right heart failure consist of fluid accumulating in parts of the body.
• Biventricular heart failure (congestive cardiac failure - CCF)?


  either due to same pathological process on each side of heart OR consequence of left heart failure leading to volume overload of pulmonary circulation, eventually causing right heart failure.

  clinical symptoms and signs of both
• Classification of heart failure?

  • Class I: no limitation of physical activity
  • Class II: Slight limitation of ordinary activity
  • Class III: marked limitation, even during less-than-ordinary activity
  • Class IV: severe limitation with symptoms at rest
• Loop diuretics to treat LVSD (left ventricular systolic dysfunction)?

  examples: Frusemide, bumetanide

  mechanism: inhibit Na+ reabsorption from the proximal tubule, hence limit water reabsorption

  side effects, can lead to:

  electrolyte abnormalities

  low blood pressure

  hypovolaemia, diminished renal perfusion
• Mineralocorticoid receptor agonists to treat LVSD?

  examples: eplerenone, spironolactone

  mechanism: promote Na+ excretion and K+ reabsorption. act on distal tubule (as opposed to proximal tubule in loop diuretics).

  difference is that mineralocorticoid receptor agonists keep potassium, whereas loop diuretics lose it in the process of excreting Na+.

  have effects outside the kidney - reduce hypertrophy and fibrosis

  side effects:

  gynaecomastia (painful excess breast tissue growth)

  electrolyte abnormalities (high K+)

  low blood pressure
• Mineralocorticoid receptor agonist examples?

  eplerenone, spironolactone
• Loop diuretics examples?

  Furosemide, Bumetanide